At last 250 people have been killed in a new massacre committed by the Syrian forces in al-Tremsa in Hama on Thursday, Al Arabiya reported citing Syrian activists.

Activists at the Syrian Revolution Commission told Al Arabiya that scores of dead bodies were scattered in houses and in farms in al-Tremsa, while more than 150 dead bodies have been piled up in al-Tremsa mosque.

Activists said that helicopters have targeted the trucks carrying the humanitarian aid on their way to al-Tremsa, while the government troops shelled the village using tanks and missiles.

The Syrian National Council called for a U.N. Security Council emergency meeting over the new massacre in al-Tremsa and urged the U.N. observers to head to the village to document the mass killing.

The Syrian state TV, meanwhile, said that “terrorists” have committed the massacre and that the Syrian government forces have entered the village only after the residents asked for their help.

“Every month, there is a major attack somewhere in Hama province, while arbitrary detentions happen every day,” the activist said.

Former head of the Syrian National Council Burhan Ghalioun told Al Arabiya that the “Syrian regime is desperate and is trying to put an end to the crisis through massacres.” He called for “real armament” for the Free Syrian Army.

Is there a massacre?

As the massacre was being committed in Syria, the major powers were holding talks at the U.N. Security Council on the Syria resolution with Russia declaring a “red line” against sanctions.

According to Al Arabiya correspondent to the United Nations Talal al-Haj, the Chinese ambassador to the U.N. said that he didn’t hear anything about a massacre being committed in Syria.

As the German ambassador to the U.N. saw a big gap in the talks, the British ambassador expressed optimism over the talks that would be resumed on Friday, Al Arabiya correspondent said.

Moscow to use veto to block Syria resolution

Russia and the Western nations on the 15-member council have drafted rival resolutions on Syria.

Britain, the United States, France and Germany have demanded sanctions against President Assad under Chapter VII of the U.N. Charter. Russia is firmly against.

Moscow said on Thursday it will not support a draft U.N. Security Council resolution on Syria that would allow the council to authorize sanctions ranging from diplomatic and economic sanctions to military intervention.

“If they decide to do it (put the resolution to a vote on Thursday), knowing it would be unacceptable to us, we will not let it pass,” Russian Deputy Foreign Minister Gennady Gatilov told Interfax news agency.

Gatilov added he did not expect there to be a vote as soon as Thursday: “The process of consultations is only just starting and should take some time,” he said.

“As a whole, their resolution is unbalanced and foresees that obligations should only be fulfilled by the Syrian government. Practically nothing is said about the obligations of the opposition,” he said.

He objected that the resolution links an extension of the mandate of the U.N. mission in Syria -- which Russia supports -- with the introduction of sanctions if the Syrian government does not fulfill certain conditions.

“We will try to move to a constructive text for a possible draft resolution which can reflect the true situation,” Gatilov said.

“Anything can be negotiated but we do not negotiate this. This is a red line,” Russia’s deputy U.N. ambassador Igor Pankin told reporters earlier at the Security Council after the first talks among key envoys.

Russia and China have previously twice used their powers as permanent members of the Security Council to veto resolutions which hinted at sanctions.

The ambassadors from all 15 council countries were to meet later Thursday to discuss the two texts.

The Security Council has to pass a resolution by July 20 when the 90-day mandate for the nearly 300 unarmed U.N. monitors in Syria runs out.

A ceasefire brokered by U.N.-Arab League envoy Kofi Annan has never taken hold and the monitors suspended their operations a month ago because of the growing danger.

Syrian activists say that more than 17,000 people have died in the 16-month old conflict.

Russia has proposed a resolution which would simply roll over the mandate for the U.N. Supervision Mission in Syria for another three months.

The Western nations want the Security Council to give Assad a 10-day deadline to halt attacks by heavy weapons or face sanctions.

Syrian regime losing grip on power

Meanwhile, the White House said on Thursday that the defection of a Syrian ambassador showed that desperation was growing within President Assad’s government and was a further sign that he was losing his grip on power.

“Those around him, both in his inner circle and more broadly in the military and governmental leadership are beginning to assess Assad's chances of remaining in power ... and making the choice that they will abandon him in favor of the Syrian people,” White House spokesman Jay Carney told reporters.

Nawaf al-Fares, who was Syria’s ambassador to Iraq, posted a video statement on Facebook that called on the army to “turn your guns on the criminals” of the government. Carney said he could not confirm reports that Fares was now in Qatar.